A 272-ha grove of dominant Microberlinia bisulcata (Caesalpinioideae) adult trees ≥50 cm stem diameter was mapped in its entirety in the southern part of Korup National Park, Cameroon. The approach used an earlier-established 82.5-ha permanent plot with a new surrounding 50-m grid of transect lines. Tree diameters were available from the plot but trees on the grid were recorded as being ≥50 cm. The grove consisted of 1028 trees in 2000. Other species occurred within the grove, including the associated subdominants Tetraberlinia bifoliolata and T. korupensis. Microberlinia bisulcata becomes adult at a stem diameter of c. 50 cm and at an estimated age of 50 y. Three oval-shaped subgroves with dimensions c. 850 m×1350 m (90 ha) were defined. For two of them (within the plot) tree diameters were available. Subgroves differed in their scales and intensities of spatial tree patterns, and in their size frequency distributions, these suggesting differing past dynamics. The modal scale of clumping was 40–50 m. Seed dispersal by pod ejection (to c. 50 m) was evident from the semi-circles of trees at the grove's edge and from the many internal circles (100–200 m diameter). The grove has the capacity, therefore, to increase at c. 100 m per century. To form its present extent and structure, it is inferred that it expanded and infilled from a possibly smaller area of lower adult-tree density. This possibly happened in three waves of recruitment, each one determined by a period of several intense disturbances. Climate records for Africa show that 1740–50 and 1820–30 were periods of drought, and that 1870–1895 was also regionally very dry. Canopy openings allow the light-demanding and fast-growing ectomycorrhizal M. bisulcata to establish, but successive releases are thought to be required to achieve effective recruitment. Nevertheless, in the last 50 y there were no major events and recruitment in the grove was very poor. This present study leads to a new hypothesis of the role of periods of multiple extreme events being the driving factor for the population dynamics of many large African tree species such as M. bisulcata.

We studied the avian foraging ecology in a single montane forest of northern Kenya, analysing the pattern of seasonal variation (wet vs. dry period) and its relationship with habitat structure. The foraging behaviour of 28 species was described in terms of four major dimensions (i.e. foraging technique, food substrate, perching site and perching height). Seasonal rainfall produced an increase in vegetation growth in the lower vegetation layers, while fruiting and flowering peaked in the dry season. We did not find much seasonal variation in foraging ecology when we analysed our data at the species or at the community levels. At the guild level, however, we found some seasonal shifts in perching height, food substrate and foraging technique. Some of these shifts seemed to be determined by food availability and distribution, as omnivores increased fruit consumption when this resource was more abundant, and nectarivores tracked the vertical distribution of flowers. The vertical biomass distribution of this avian community seemed to be largely determined by food. However, seasonal variation in the total biomass of some guilds was probably related to factors not considered in this study, such as breeding, or intra-African migratory movements. Altogether, despite marked seasonal variation in vegetation structure and food resources, the bird assemblage showed little change in its feeding ecology and micro-habitat use. Hence, we suggest that changes in habitat structure and resource levels were coped with primarily by adjusting population density and food requirements through seasonal breeding or migration.

Tropical pioneer tree species are considered as a functional group characterized by a suite of ecological characteristics such as high light demand and high photosynthetic capacities. This study compared the photosynthetic characteristics of eight co-existing pioneer tree species in 3–4-y-old and about 6-m-tall secondary forest stands in Sulawesi, Indonesia. Its objectives were (1) to determine the range and interspecific variation in six photosynthetic parameters, and (2) to identify morphological and chemical leaf traits that can predict light-saturated net photosynthetic rates (on a leaf area or leaf mass basis, Amax-area or Amax-mass). Species averages of Amax-area in sun leaves ranged between 14.2 and 20.3 μmol m−2 s−1 (mean 17.5) which is high compared with literature data. Among the co-existing species, average leaf size (56–896 cm2) differed by a factor of 16, specific leaf area (SLA, 10.7–21.4 m2 kg−1) and leaf nitrogen content (19.6–33.9 g kg−1) twofold. At the species level, Amax-area was not correlated with leaf N content but decreased significantly with leaf size. Amax-mass showed a higher interspecific variation than Amax-area, and was positively correlated with SLA and leaf N content (slope: 13.4 nmol CO2 g N−1 s−1). Both, Amax-area and Amax-mass were more closely related to leaf morphological attributes than to leaf N. We conclude that the tropical pioneer tree species studied do not form a homogeneous functional group in terms of photosynthetic performance. Rather, a considerable variation in leaf morphology and nitrogen content exists, which also shows up in a substantial variation in Amax-mass and, to a lesser extent, in Amax-area.

The analysis of beta diversity (inter-habitat diversity) of very species-rich and incompletely sampled tropical arthropod communities requires the choice of appropriate statistical tools. The performance of the three commonly employed ordination methods, correspondence analysis (CA), detrended correspondence analysis (DCA), and non-metric multidimensional scaling (NMDS), was compared on a large empirical data set of geometrid moths sampled along an altitudinal gradient in an Andean montane rain forest. Despite the high species richness and incompleteness of the ensembles, all methods depicted the same, readily interpretable patterns. Both CA and NMDS showed an arch-like structure, which hints at an underlying coenocline, whereas this arch was computationally eliminated in DCA. For this particular data set, CA and NMDS both provided convincing results while the detrending algorithm of DCA did not improve the interpretability of the data. Of the large number of similarity indices available to be used in combination with NMDS, the binary Sørensen and the abundance-based Normalized Expected Species Shared (NESS) index were tested. Performance of the indices was measured by comparing stress, a measure of poorness-of-fit in NMDS. NMDS ordinations with lowest values of stress were achieved by the NESS index with the parameter m set to its maximum (mmax). In contrast, ordinations based on NESS values with the parameter m set to 1 (identical with Morisita's index), had consistently higher stress values and performed worse than ordinations using Sørensen's index. Hence, if high values of m can be achieved in similar data sets, the NESS index with mmax is recommended for ordination purposes and Morisita's index should be avoided.

Controls over net primary productivity are the subject of a long-term experiment within a lowland subtropical wet forest in the Luquillo mountains of Puerto Rico. Responses of the fern community to fertilization and debris-removal treatments and to monitoring activities were assessed 6 y after the experiment began in October 1989, just after the passage of Hurricane Hugo. Negative fern responses to fertilization included a qualitative change in species composition and a 13-fold reduction in density compared with controls. Plants were smaller and spore production rates were lower. Debris removal reduced the number of species and increased the proportion of terrestrial species. Density of Nephrolepis rivularis individuals in debris-removal plots was only 5% that of control levels while abundance of Thelypteris deltoidea nearly doubled. Buffer-zone fern density was 36% greater than and per cent of leaves damaged was half that of the monitored zones. The magnitude of the responses of ferns to experimental treatments and to monitoring effects suggest that they may be good early indicators of change in a tropical forest.

We investigated the relative influences of vegetation cover, invertebrate biomass as an index of food availability and the short-term effects of fires on the spatial variation in densities of the rodent Bolomys lasiurus in an Amazonian savanna. Densities were evaluated in 31 plots of 4 ha distributed over an area of approximately 10×10 km. The cover of the tall grass (Trachypogon plumosus), short grass (Paspalum carinatum), shrubs and the extent of fire did not explain the variance in densities of Bolomys lasiurus. Food availability alone explained about 53% of the variance in B. lasiurus densities, and there was no significant relationship between insect abundance and vegetation structure. Fires had little short-term impact on the density of Bolomys lasiurus in the area we studied. As the species appears to respond principally to food availability, habitat suitability models based on easily recorded vegetation-structure variables, or the frequency of disturbance by fire, may not be effective in predicting the distribution of the species within savannas.

Epiphytes are one of the most ubiquitous elements of tropical forest canopies, including seasonally dry tropical forests. Given the temporal variation in weather conditions in the latter, epiphyte populations may be subject to wide temporal variation in seedling recruitment, reproductive success, vegetative propagation and mortality rate. In this study, we use a 3-y demographic data set for Tillandsia brachycaulos to project its long-term population dynamics through the use of average and periodic matrices, as well as stochastic simulations. The results show that demographic behaviour varied over the 3 years of study, apparently in relation to rainfall. The first 2 years yielded a low λ value (0.79 and 0.80 – although only the former was significantly lower than unity), while the third year resulted in a λ = 1.08 (not significantly different from 1.0). When incorporating this demographic variation in an average matrix, a periodic matrix and stochastic simulations, the resulting overall λ was below unity in all three cases. The projections of the stochastic simulations suggest that the population would be able to persist in the long run only if the frequency of “good” years (defined here as those with an August rainfall above 200 mm) was above 0.6, which appears unlikely given that global warming might result in a lower frequency of rainy years in tropical dry forests.

Extrafloral nectar is an indirect, generally ant-mediated, defence mechanism that is particularly common in tropical plants. This study focuses on interactions among different groups of arthropods visiting extrafloral nectaries of the South-East Asian myrmecophilic plant, Macaranga tanarius. The diurnal activity patterns of arthropods on nectaries were recorded on two occasions, each plant being used once in an untreated state and once after chemical induction of extrafloral nectar flow. Ants, widely regarded as the most important consumers of extrafloral nectar, made up only 60% of all nectary-visiting arthropods. Striking negative relations became obvious between ants and ‘non-ants’, among which two (morpho)species of fly (Grammicomya sp. and Mimegralla sp., both Micropezidae) were most important. On most leaves, either ants or ‘non-ants’, but not both groups, were present at one time. Behavioural observations revealed that many flies actively excluded other arthropods, including ants, from the nectaries or leaves. However, the flies had no detectable defensive effect against herbivores. The presence of these ‘thieves’ of extrafloral nectar therefore can cause ecological costs in terms of reduced presence of ants that consume extrafloral nectar and defend plants.

Soil water content and above-ground biomass accumulation, above 10 cm high, were measured monthly in a flooded savanna ecosystem under grazing pressure and under cattle exclusion, during two growth cycles. Near-to-the-ground and below-ground biomass were measured three times during this period. Besides, composition, species richness and diversity were obtained through a floristic inventory. Despite a relatively high floristic richness and diversity, Panicum laxum is the dominant species throughout the study area, while three other perennial grasses, Paspalum chaffanjonii, Leersia hexandra and Axonopus purpusii, also reach high values of cover and biomass. Each of them reacts specifically to flooding, drought and grazing conditions. This ecosystem shows a strongly seasonal behaviour, with primary production, mortality and decomposition sharply timed by soil relative water content. Both drought and water excess seem to limit plant production, even more during wet years when the savanna might remain flooded for up to 4 mo. Some structural and functional differences between the grazed and the protected systems are demonstrated, but under the actual, relatively low stocking rate, the grazed savanna produces as much forage as the ungrazed one.

Fine roots and their turnover represent a dynamic aspect of below-ground biomass (BGB) and nutrient capital in forest ecosystems, and account for a significant fraction of net primary productivity (NPP) (Cuevas 1995, Vogt et al. 1990). On a weight basis, coarse roots contribute more to total ecosystem biomass than fine roots, but they account for only a small portion of annual root production (Eamus et al. 2002). Despite the fact that fine roots may compose less than 2% of total ecosystem biomass, they may contribute up to 40% of total ecosystem production (Vogt et al. 1990). Therefore, estimates of root production, like estimates of root biomass, should differentiate between coarse- and fine-root production.

Habitat fragmentation causes a sharp increase in the forested area affected by edge effects (Murcia 1995). Compared with the core of the forest, edges present higher litterfall rates, air and soil humidity reduction, higher temperature and increased wind incidence (Bierregaard et al. 1992, Didham & Lawton 1999, Laurance et al. 1998, Matlack 1993). These features of edges may increase the probability of fire occurrence, especially if the surrounding vegetation is composed of grasses (D'Antonio & Vitousek 1992, Freifelder et al. 1998). After a fire, the damaged edge will grow substantial amounts of herbaceous vegetation, extending the inflammable area into the forest, and thereby creating a positive feedback system of fire susceptibility and intensity (Cochrane & Schulze 1999, Cochrane et al. 1999). Fires may affect the structure and composition of the vegetation (Cochrane & Schulze 1999, Didham & Lawton 1999, Sanaiotti & Magnusson 1995), favouring, in the long-term, the dominance of the community by species characteristic of disturbed habitats and making the habitat unsuitable to primary forest species (Malcolm 1994, Possingham et al. 1994). Unfortunately, there are few studies on the effects of fires on neotropical small-mammal populations (Borchert & Hansen 1983, Ojeda 1989, Vieira & Marinho-Filho 1998). The objective of this study was to analyse the influence of a fire on populations of two rodent species, Akodon cursor (Winge) and Oecomys concolor (Wagner) in two fragments of Atlantic Forest in Brazil.

Many rain-forest trees in South-East Asia, including the dominant canopy family Dipterocarpaceae, reproduce in gregarious mast-fruiting events once every 2–11 y (Ashton et al. 1988). The dominant hypothesis for the evolution of masting is that predators are incapable of consuming mast seed crops, so that natural selection has favoured parent trees that fruit in synchrony (Janzen 1974, 1976). Mast flowering and fruiting are visually spectacular and quantified in harvest records for dipterocarp species producing large, oil-rich tengkawang seeds (Curran et al. 1999). Seedling recruitment following a mast is less obvious and has no immediate commercial value. However, a number of pulses of recruitment have been documented (Ashton et al. 1988, Chan 1980, Fox 1972, Liew & Wong 1973). These, together with general acceptance of the satiation hypothesis, have led to the widespread assumption that masts reliably increase seedling density and generate distinct seedling cohorts (Whitmore 1998). Indeed, foresters in Malaysia and Indonesia often recommend harvesting only after a mast, to ensure high densities of seedling regeneration.

Figs (Ficus species) are an important resource for a diverse array of organisms in most tropical forests (Janzen 1979 but see Gautier-Hion & Michaloud 1989). The inflorescence of Ficus, hereafter referred to as the ‘fig’, is an enclosed receptacle lined with unisexual flowers. The flowers of Ficus species are pollinated by wasps that feed on galled fig ovules as larvae and that lay eggs in fig flowers as adults (Weiblen 2002). Ripe figs are consumed by vertebrate frugivores, which are the primary dispersers of fig seeds (Shanahan et al. 2001). The interaction between figs, pollinators and frugivores introduces the potential for conflict between the roles of raising fig wasps and dispersing seeds. Specifically, the pollination mutualism could be compromised if frugivores consumed figs containing pollinator larvae. This conflict is resolved in very different ways according to the breeding system of the fig.

Relatively little is known of the relationships between many lepidopteran species and their larval food plants in tropical rain forests, compared with temperate ecosystems. Species are often known only from the adult form, and the larvae and aspects of ecology, host plant, etc. are unknown (Williams 1971). Many species in the moth genus Achaea sometimes occur at high enough population densities to be defoliators, and several species are associated especially with forest trees: some are agricultural pests on groundnuts and castor oil plant (Ricinus communis) (Pinhey 1975, M. Shaw, pers. comm.). Achaea catocaloides occurs from West Africa through Uganda to East Africa (Seitz 1925) and has been recorded in interactions with ants in Cameroon (Dejean et al. 1991).

In fragmented tropical landscapes, among the most pervasive causes of ecological change are edge effects – diverse ecological alterations associated with the abrupt, artificial boundaries of forest fragments (Laurance & Bierregaard 1997, Lovejoy et al. 1986, Turner 1996). A striking edge effect in fragmented Amazonian forests is chronically elevated tree mortality (Ferreira & Laurance 1997, Laurance et al. 1998a). Large (> 60 cm diameter) trees are especially vulnerable to fragmentation, dying three times faster within 300 m of edges than in forest interiors (Laurance et al. 2000). Elevated tree mortality alters canopy-gap dynamics, promotes a proliferation of disturbance-adapted successional species (Laurance et al. 1998b), reduces above-ground biomass (Laurance et al. 1997), and accelerates litter production (Didham & Lawton 1999, Sizer et al. 2000) and carbon cycling (Nascimento & Laurance, in press).